This invention relates to polyolefin graft copolymers.
Polyolefins are relatively inexpensive and are superior in processability, toughness, water resistance, organic solvent resistance, and chemical resistance. However, they lack stability toward an oxidizing environment and are deficient in surface properties such as coefficient of friction and scratch and mar resistance, as well as in oxygen barrier properties.
Fluorinated polymers are characterized by resistance to harsh chemicals as well as stability toward heat, ultraviolet light, high energy radiation, and oxidation. Polyvinylidene fluoride, a member of the class of fluorinated polymers, is a semi-crystalline material with a high dielectric constant that can easily be processed on conventional molding and extrusion equipment. It also has high mechanical and impact strength, and high resistance to creep, fatigue and abrasion. Film made from this polymer has excellent oxygen and moisture barrier properties.
Graft copolymers of polyolefins are of interest because they are capable of possessing some properties of the polymerized grafting monomer as well as of the polyolefin backbone.
U.S. Pat. Nos. 4,806,581 and 4,605,704 disclose a process for making graft copolymers in which liquid monomer and initiator are absorbed into solid polyolefin particles, followed by reaction of the monomer in the particles to produce polymer and graft copolymer simultaneously in the same reactor. The grafting monomers include vinyl monohalides, such as vinyl chloride, and dihalides, such as vinylidene fluoride, which can be mixed with less than 50% of another monomer such as an acrylate or methacrylate ester. The resulting product can be molded to form transparent or translucent molded articles.
There is still a need for an improved process for producing graft copolymers comprising a polyolefin backbone which are useful for forming articles with improved surface and barrier properties as well as improved thermal stability.
In one embodiment of this invention, a fluorine-containing graft copolymer comprises a backbone of an olefin polymer material to which is graft polymerized (a) at least one fluorinated gaseous monomer having the formula CR1R2xe2x95x90CR3R4, where R1=H, F, or Cl; R2=H, F, or Cl; R3=H, F, CH3, CF3, or Cl, and R4=H, F, or Cl, wherein at least two fluorine atoms are present, and, optionally, (b) at least one non-fluorinated monomer selected from the group consisting of (i) vinyl-substituted aromatic, heterocyclic, and alicyclic compounds, (ii) unsaturated aliphatic nitrites, and (iii) unsaturated aliphatic monocarboxylic acids or esters thereof, wherein the total amount of monomers added is about 1 to about 100 parts per hundred parts of the olefin polymer material, and the particulate olefin polymer material has a weight average diameter of about 0.4-7 mm, a surface area of at least 0.1 m2/g, and a pore volume fraction of at least about 0.07, and wherein more than 40% of the pores in the particle have a diameter greater than 1 micron.
This graft copolymer is prepared by a process comprising, in a non-oxidizing atmosphere:
(1) treating a particulate olefin polymer material at a temperature of about 10xc2x0 to about 70xc2x0 C. with about 0.1 to about 6.0 parts per hundred parts of the olefin polymer material, of an organic compound that is a chemical free radical polymerization initiator and has a decomposition half-life at the temperature used in step (2) of about 1 to about 240 minutes,
(2) increasing the temperature to about 60xc2x0 to about 115xc2x0 C.,
(3) adding (a) at least one fluorinated gaseous monomer having the formula CR1R2xe2x95x90CR3R4, where R1=H, F, or Cl; R2=H, F, or Cl; R3=H, F, CH3, CF3, or Cl, and R4=H, F, or Cl, wherein at least two fluorine atoms are present, and, optionally, (b) at least one non-fluorinated monomer selected from the group consisting of (i) vinyl-substituted aromatic, heterocyclic, and alicyclic compounds, (ii) unsaturated aliphatic nitrites, and (iii) unsaturated aliphatic monocarboxylic acids or esters thereof, wherein the total amount of monomers added is about 1 to about 100 parts per hundred parts of the olefin polymer material, to produce and maintain a pressure of about 200 to about 900 psi
(4) heating at a temperature within the range specified in step (2) for about 1 to about 6 hours,
(5) cooling to room temperature, and
(6) releasing the pressure to remove unreacted monomer,
wherein the particulate olefin polymer material has a weight average diameter of about 0.4-7 mm, a surface area of at least 0.1 m2/g, and a pore volume fraction of at least about 0.07 and wherein more than 40% of the pores in the particle have a diameter greater than 1 micron.
In another embodiment, a fluorine-containing graft copolymer is prepared in a non-oxidizing environment by:
(1) heating a peroxidized olefin polymer material to a temperature of about 60xc2x0 to about 140xc2x0 C.,
(2) adding (a) at least one fluorinated gaseous monomer having the formula CR1R2xe2x95x90CR3R4, where R1=H, F, or Cl; R2=H, F, or Cl; R3=H, F, CH3, CF3, or Cl, and R4=H, F, or Cl, wherein at least two fluorine atoms are present, and, optionally, (b) at least one non-fluorinated monomer selected from the group consisting of (i) vinyl-substituted aromatic, heterocyclic, and alicyclic compounds, (ii) unsaturated aliphatic nitriles, and (iii) unsaturated aliphatic monocarboxylic acids or esters thereof, wherein the total amount of monomers added is about 1 to about 100 parts per hundred parts of the olefin polymer material, to produce and maintain a pressure of about 200 to about 900 psi
(3) heating at a temperature within the range specified in step (1) for about 1 to about 6 hours,
(4) cooling to room temperature, and
(5) releasing the pressure to remove unreacted monomer.
Another embodiment of this invention comprises a fluorine-containing graft copolymer comprising an olefin polymer backbone to which is graft polymerized about 1 to about 120 parts per hundred parts of the olefin polymer material, of (a) at least one fluorinated monomer having the formula CH2xe2x95x90C(R1)xe2x80x94(COOR2), where R1=H, CH3, or CF3, and R2 is H or a partially or completely fluorinated C1-C12 alkyl group, and, optionally, (b) at least one non-fluorinated monomer selected from the group consisting of (i) vinyl-substituted aromatic, heterocyclic, and alicyclic compounds, (ii) unsaturated aliphatic nitrites, and (iii) unsaturated aliphatic monocarboxylic acids or esters thereof.
This graft copolymer is prepared by a process comprising, in a non-oxidizing atmosphere:
(1) treating a particulate olefin polymer material at a temperature of about 60xc2x0 C. to about 125xc2x0 C. with about 0.1 to about 6.0 parts per hundred parts of the olefin polymer material, of an organic compound that is a chemical free radical polymerization initiator and has a decomposition half-life at the temperature used of about 1 to about 240 minutes;
(2) treating the olefin polymer material at the temperature selected over a time period that coincides with or following (1), with or without overlap, with (a) at least one fluorine-containing monomer having the formula CH2xe2x95x90C(R1)xe2x80x94(COOR2), where R1=H, CH3, or CF3, and R2 is H or a partially or completely fluorinated C1-C12 alkyl group, and, optionally, (b) at least one non-fluorinated monomer selected from the group consisting of (i) vinyl-substituted aromatic, heterocyclic, and alicyclic compounds, (ii) unsaturated aliphatic nitrites, and (iii) unsaturated aliphatic monocarboxylic acids or esters thereof, wherein the total amount of monomers added is about 1 to about 120 parts per hundred parts of the olefin polymer material, the monomer being added to the olefin polymer material over a time period from 5 minutes to 3-4 hours to provide a rate of addition that is less than about 4.5 pph per minute at any addition level; and thereafter
(3) simultaneously or successively, in any order, removing any unreacted monomer from the resulting grafted particulate olefin polymer material, and decomposing any unreacted initiator and deactivating any residual free radicals in the material.
Another embodiment of the invention is a fluorine-containing graft copolymer comprising a backbone of an olefin polymer material to which is graft polymerized a combination of:
(a) at least one fluorinated gaseous monomer having the formula CR1R2xe2x95x90CR3R4, where R1=H, F, or Cl; R2=H, F, or Cl; R3=H, F, CH3, CF3, or Cl, and R4=H, F, or Cl, wherein at least two fluorine atoms are present,
(b) at least one fluorinated monomer having the formula CH2xe2x95x90C(R1)xe2x80x94(COOR2), where R1=H, CH3, or CF3, and R2 is H or a partially or completely fluorinated C1-C12 alkyl group, and, optionally,
(c) at least one non-fluorinated monomer selected from the group consisting of (i) vinyl-substituted aromatic, heterocyclic, and alicyclic compounds, (ii) unsaturated aliphatic nitrites, and (iii) unsaturated aliphatic monocarboxylic acids or esters thereof,
wherein the total amount of polymerized monomers is about 1 to about 100 parts per hundred parts of the olefin polymer material.
This graft copolymer is prepared in a non-oxidizing environment by:
(1) treating a particulate olefin polymer material at a temperature of about 10xc2x0 to about 70xc2x0 C. with about 0.1 to about 6.0 parts per hundred parts of the propylene polymer material, of an organic compound that is a chemical free radical polymerization initiator and has a decomposition half-life at the temperature used in step (2) of about 1 to about 240 minutes,
(2) increasing the temperature to about 60xc2x0 to about 115xc2x0 C.,
(3) adding a combination of:
(a) at least one fluorinated gaseous monomer having the formula R1R2xe2x95x90CR3R4, where R1=H, F, or Cl; R2=H, F, or Cl; R3=H, F, CH3, CF3, or Cl and R4=H, F, or Cl, wherein at least two fluorine atoms are present, to produce and maintain a pressure of about 200 to about 900 psi,
(b) at least one fluorinated monomer having the formula CH2xe2x95x90C(R1)xe2x80x94(COOR2), where R1=H, CH3, or CF3, and R2 is H or a partially or completely fluorinated C1-C12 alkyl group, and, optionally,
(c) at least one non-fluorinated monomer selected from the group consisting of (i) vinyl-substituted aromatic, heterocyclic, and alicyclic compounds, (ii) unsaturated aliphatic nitrites, and (iii) unsaturated aliphatic monocarboxylic acids or esters thereof,
wherein the total amount of monomers added is about 1 to about 100 parts per hundred parts of the olefin polymer material,
(4) heating at a temperature within the range specified in step (2) for about 1 to about 6 hours,
(5) cooling to room temperature, and
(6) releasing the pressure to remove unreacted monomer.
The graft polymerized fluorine-containing monomers are found at the surface of articles made from the graft copolymers of this invention as well as in the inside of the article, thereby reducing the coefficient of friction and improving scratch and mar resistance and oxygen barrier properties. The thermal oxidative stability of the polymer is also improved by the presence of the polymerized fluorinated monomers.